Percutaneous Valve Therapy (PVT), as currently under development by Edwards Lifesciences and Medtronic CoreValve, holds the promise of relieving critical aortic valve stenosis with a minimally invasive, “beating heart” procedure.
More particularly, in patients with critical aortic valve stenosis, the native valve's leaflets are generally calcified so that the effective area of the valve is greatly reduced, e.g., to an effective area of less than 1 cm2. As a result, valve function is significantly impaired and the flow of oxygenated blood to the body is greatly reduced.
Percutaneous valve therapy (PVT) offers one promising solution to critical aortic valve stenosis. More particularly, with PVT, the diseased native valve is first manipulated so as to increase its flow area. This is typically done via valvuloplasty, where a stiff balloon is inflated inside the native valve so as to swage the leaflets open, thereby relieving the stenosis. Next, a prosthetic aortic valve is percutaneously deployed (e.g., endoluminally or via a thoracotomy) at the site of the native aortic valve, while the heart is still beating, in order to replace the malfunctioning natural aortic valve.
While PVT offers substantial advantages over a conventional “open heart” aortic valve replacement, it still suffers from a number of serious problems. More particularly, to date, deployment of percutaneous valves to the diseased native valve site has resulted in serious complications, such as:
1. Conduction system damage (i.e., damage to the electrical system of the heart), typically requiring installation of a permanent pacemaker (occurring in approximately 7% of patients);
2. Stroke (occurring in approximately 2.5% of patients);
3. Significant aortic regurgitation (occurring in approximately 4.7% of patients);
4. Valve malposition (occurring in approximately 1.5% of patients);
5. The need for conversion to conventional “open heart” surgery during the percutaneous procedure (occurring in approximately 2.7% of patients); and
6. Coronary obstruction (occurring in approximately 0.6% of patients).
The evolution of percutaneous valve deployment methods, as is well documented in the literature, has progressed in the following order:
1. “Antegrade deployment”, where the prosthetic valve is advanced up through the venous system and across the septum of the heart to the native valve location. This method is generally no longer practiced.
2. “Retrograde deployment”, where the prosthetic valve is advanced up from the femoral artery, over the aortic arch, to the native valve location.
3. “Transapical deployment”, where the prosthetic valve is advanced through the apex of the heart, into the left ventricle and up to the native aortic valve location. Note that a thoracotomy is required in order to access the apex of the heart.
While PVT complication rates have slowly declined, the inherent disadvantages of manipulating the diseased native valve, and then deploying the prosthetic valve to the native valve location, are inescapable.
A known alternative to both conventional “open heart” aortic valve replacement, and to the aforementioned percutaneous valve therapy (PVT), is aortic valve bypass. In aortic valve bypass, a bypass conduit, having a prosthetic valve incorporated therein, is deployed between the left ventricle of the heart and the descending aorta. See, for example, FIG. 1. See also U.S. Pat. No. 7,510,561, issued Mar. 31, 2009 to Richard M. Beane et al. for APPARATUS AND METHOD OF CONNECTING A CONDUIT TO A HOLLOW ORGAN, which patent is hereby incorporated herein by reference.
As currently practiced, aortic valve bypass is a proven procedure that can relieve critical aortic stenosis without the aforementioned complications of percutaneous valve deployment to the native valve site (i.e., without the complications associated with PVT).
A drawback of current aortic valve bypass therapy, however, is the approximately 6″-8″ thoracotomy incision which is required in order to gain access to the left ventricle of the heart and to the descending aorta, which is required in order to install the bypass conduit. As a result, aortic valve bypass cannot currently be considered to be a minimally invasive procedure, due to the need to provide a thoracotomy of such size. Also, when the ribs are spread to create access to the thoracic cavity, the ribs can sometimes fracture, thereby causing additional trauma to the patient.
Consequently, there is a need for an improved procedure to relieve critical aortic stenosis.